I highly recommend Annarasumanara as an example webtoon that takes full advantage of the vertical format:
https://www.webtoons.com/en/drama/annarasumanara/ep-1/viewer...
https://www.webtoons.com/en/drama/annarasumanara/ep-1/viewer...
But for some reason, I find vertical scrolling to be tedious and annoying. My 13" rMBP is at default scaling, so I only have 800px in total height, and about 720px for the web page area. It's really irritating seeing so little and having to constantly scroll. Horizontal there's an extra 560px, or 77% more.